1. Field of the Invention
The present invention relates to a tire pressure gauge, and more particularly to a digital pressure gauge with visual and voice response system for measuring the air pressure of a tire.
2. Description of the Prior Art
It is extremely important for driving safety to ensure that the tires of an automobile or motorcycle normally function. The air pressure of the tire is a major factor determining whether the tire can normally function.
In order to measure the tire pressure, in addition to visual observation, a tire pressure gauge is generally used to more precisely measure the tire pressure.
The conventional tire pressure gauges may be in the form of analog type and digital type. The digital type tire pressure gauge is able to directly convert the measured tire pressure into numerals. Accordingly, a user can conveniently read accurate tire pressure from a display of the tire pressure gauge.
An example of a prior art tire gauge is disclosed in U.S. Pat. No. 5,394,343, issued Feb. 28, 1995, issued to Tsao, entitled xe2x80x9cElectronic Tire Gaugexe2x80x9d. This prior art invention provides an electronic tire pressure gauge comprising a pressure transducer, a voltage controlled oscillator, a comparator, a clock, a microprocessor, and a display. The display is capable of displaying a numerical value of the measured pressure of the tire.
Another example of the prior art tire gauge is disclosed in U.S. Pat. No. 4,250, 759, issued Feb. 17, 1981, issued to Vago et al., entitled xe2x80x9cDigital Readout Gaugexe2x80x9d. This prior art invention provides a digital tire gauge mainly comprising a pressure transducer, a peak detector, an analog-to-digital converter, and a display.
It is noted that the conventional digital type tire pressure gauges can only display the tire pressure by numerals, so that in some situations such as deflected observation position, insufficient illumination, failing to directly see with eyes, etc., the user will be unable to visually obtain the tire pressure.
Moreover, it is very important to periodically service the tire for ensuring safety in use of vehicles, especially with respect to heavy vehicles. However, users of automobiles and motorcycles often neglect to periodically check the tire.
It is thus desirable to have a digital tire pressure gauge with visual and voice response for overcoming the problems discussed above.
It is therefore a primary object of the present invention to provide a tire pressure gauge with function of digital display of tire pressure. In cooperation with the digital display, a speech indicative of the tire pressure is simultaneously emitted, whereby under a circumstance that a user can hardly visually observe the displayed tire pressure value, the user can still know the tire pressure value via the speech indication.
It is a further object of the present invention to provide a tire pressure gauge which not only has functions of digital display and speech indication of the tire pressure value, but also has a function of timed reminding. Therefore, when a predetermined time is reached, a vehicle-user is reminded to check whether the tire pressure in normal so as to ensure safety in driving.
To achieve the above objects, in accordance with the present invention, there is provided a digital tire pressure gauge with an electronic control circuit for measuring the air pressure of the tire. The electronic control circuit comprises a pressure transducer, a pair of switching units, an integrator for receiving the analog output signal of the pressure transducer and then generating a triangular waveform signal with an increasing ramp section and a decreasing ramp section under control of the first and second switching units, a comparator used to compare the triangular waveform signal of the integrator with a reference signal and then generate an output signal with a wave width corresponding to the increasing ramp section of the output signal of the integrator, a register for temporally storing the output signal of the comparator, a peak value detector, a holding circuit, a counting pulse generating circuit, a counting circuit, and a pressure value output buffer. A display mounted on the tire gauge is used to display the pressure value stored in the output buffer. A speech processing circuit is used to generate a speech signal accompanying with the display of the visual pressure value signal displayed on the display. Further, a timer circuit may be coupled to the speech processing circuit for generating an actuating signal at preset regular intervals for triggering the speech processing circuit to play a predetermined reminding speech.